Japanese Math Quiz Outrages Netizens

The photo above, taken at a Japanese elementary school 3 years ago, is the cause of great discussion once again. The math problem in question, 9 ÷ 0, has been debated and re-tweeted thousands of times. Schools in America teach the solution to the above problem as "undefined," and many netizens are–what else?–outraged that the error could be overlooked by the teacher. Others wonder if the problem is fair, or if it even has an answer. How would you answer the problem above? Did you learn this kind of problem in elementary school?
Source: news.infoseek.co.jp